To grow a silicon single crystal based on the CZ method, such a silicon single crystal pulling apparatus as shown in FIG. 9 has been conventionally used.
As shown in FIG. 9, this pulling apparatus 101 has a chamber 102, a crucible 103, crucible-adjusting means 105 for rotating/moving up and down the crucible 103, and a heater 106. Further, the crucible 103 contains a silicon melt 108 molten by the heater 106, and a silicon single crystal 113 is grown by immersing a seed crystal 112 held at a lower end of a wire 111 suspended from the upper side of the chamber 102 in the silicon melt 108 and pulling the seed crystal 112. During pulling, an inert gas is flowed in the chamber 102, and a gas flow-guide cylinder 110 for this purpose is also provided.
As described above, in manufacture of a silicon single crystal including the inert gas flow-guide cylinder in the chamber, for example, a distance from an end of the gas flow-guide cylinder to a silicon melt surface and others must be accurately set. To accurately control a defect in a method for manufacturing, e.g., a defect-free crystal, a temperature gradient (G) near a solid-liquid interface in crystal growth must be controlled, and a position of the silicon melt surface must be accurately measured to execute this control.
In conventional examples, an end of a prismatic seed for manufacture of a single crystal is detected by a laser sensor, stopped at a predetermined position, and moved down from this point, and a distance to come into contact with a silicon melt surface is measured, thereby calculating an accurate position of the silicon melt surface (Patent Literature 1).